Global efforts are being made to reduce the production of green house gases due to increasing environment pollution and global warming. For example, various efforts such as expansion of use of renewable energy, development of ecofriendly vehicles, and development of a power storage system that improves power supply systems have been made.
Generally, most power supply systems are based on thermal power generation that uses fossil fuels and emits a large amount of carbon dioxide, resulting in severe environmental pollution. To solve this problem, interest in development of a power supply system which uses ecofriendly energy (wind power, solar energy, tidal power, etc.) is increasing.
Since most of the renewable energies are clean energies sources occurring in nature, they are attractive and preferable in that they produce no exhaust gas associated with environmental pollution. On the other hand, they have limits because output power thereof is highly dependent on the weather or natural environments and thus dramatically fluctuates due to changeable weather or natural environments.
Electric power storage technology is a key technology for effective use of all kinds of energy including efficient use of electric power, improvement of performance or reliability of a power supply system, and spread of use of renewable energies that highly vary with time. Therefore, future development of such a technology and contribution of the technology to the public good are highly expected. Specifically, a role of a fuel battery and usability of a fuel battery in this field are increasingly expected.
A REDOX flow battery and a fuel battery differ in terms of constituent parts but are the same in that an electrochemical reaction of a reactant occurs in a cell provided with predetermined elements to produce electric charges.
In a REDOX flow battery, an electrolyte is used as a reactant. It is stored in an additional tank and supplied, through pumping operations of a pump, to a stack in which multiple cells are stacked through a channel formed in the stack, to be distributed to the cells. At this point, a pump is used to circulate the electrolyte, which causes a predetermined pressure in the stack. Generally, an inside of the stack is furnished with an anti-leaking means (gasket, O-ring, or joint) for preventing leakage of an electrolyte. In normal state, an electrolyte flows through a tank, a pump, a pipe, and a channel formed in a stack. However, an electrolyte is likely to leak from a stack due to an internal pressure of the stack and a breakdown of a sealing portion. In this case, surrounding parts may be corroded and the amount of an electrolyte in a stack changes from a preset value, which disrupts the balance of the electrolyte.
A fuel battery has a similar structure to a REDOX flow battery. That is, a reactant is supplied to a stack composed of multiple cells. Therefore, there is also a risk that a reactant may leak from a stack and surrounding parts may be corroded.
In order to inhibit leakage of a reactant, Korean Patent Application Publication No. 10-2001-0060112, titled “Polymer Electrolyte Fuel Cell”, discloses a technology in which ribs are provided to around a gas supply-and-discharge hole of a flat panel gasket used to manufacture a unit cell or a stack and to around an electrode to prevent leakage of a gas. In addition, Korean Patent No. 10-1291752, titled “Combined Complex Electrode Cell with Inner Seal and REDOX Flow Battery Comprising the Same” discloses a technology in which a bipolar plate and a manifold are unified and a sealing structure is provided to a combined portion between the bipolar plate and the manifold to prevent electrolytes in an anode and a cathode from overflowing. However, this technology cannot guarantee long term sealing reliability due to change in physical properties and deformation.